Conventional models for energy storage suffer from poor energy densities and high cost of operation. Most common energy storage devices such as batteries use various types of designs but all eventually rely on separation of charges thereby creating an electric field or electromotive force between the positively and negatively charged regions wherein the energy is stored.
Additional conventional methods store energy in chemical bonds of substances while some others use mechanical set ups to store energy. Examples of Chemical Energy storage include Hydrogen Fuel as well as Fossil Fuels such as Gasoline. Mechanical energy storage is seen in Flywheels, Compressed Air Storage as well as Pumped Hydro.